https://preparationpoint.info/mathematics-mcqs/basic-maths-mcqs/p-q-and-r-can-do-a-work-in-20-30-and-60-days-respectively-how-many-days-does-it-need-to-complete-the-work-if-p-does-the-work-and-he-is-assisted-by-q-and-r-on-every-third-day-2/